A conventional self-closing device for a rail system is disclosed in U.S. Pat. No. 5,490,724 to Domenig, titled “Drawer guide for supporting a movable structure such as a drawer in a furniture article”, and the device discloses a rail system for slidably supporting a movable structure such as a drawer on a furniture article. The device includes a rotatable roller on a guide rail which is substantially horizontally connected to the furniture article and a movable rail which supports the movable structure. The movable rail is able to move relative to the guide rail, wherein the distal end of the guide rail has a tilt surface which is located lower than the horizontal surface so that when the movable rail moves inward to the tilt surface, the movable rail is guided by the tilt surface and retracted in the furniture article.
It is noted that the movable rail has to be retracted until the movable rail moves to the tilt surface of the distal end of the guide rail. The movable rail cannot be automatically guided to be retracted. The distance of the tilt surface usually is limited and the movable rail traveling this short distance cannot have an automatic return function. Besides, the rail system returns the movable rail by the gravity which is deemed to be not sufficient.